DE8802883U1 - Rotary potentiometer - Google Patents

Description

P r e h

Electromechanical works Jakob Preh, Nachf. GmbH A Co. Schwelnfurter Straße S Bad Neustadt/Saale, 02.03.88

02./88 GM Description

Rotary potentiometer

The invention relates to a rotary potentiometer with a cylindrical or partially cylindrical resistance track, on the two edges of which parallel to the cylinder axis at least one pair of electrodes is arranged, via which the resistance track is subjected to voltage, and with a wiper lying on the resistance track, which is held on an actuator that can be rotated about the cylinder axis.

Such a rotary potentiometer is described in EP 0 157 666 A1. This rotary potentiometer can be used to detect an angular position of a rotating component, for example a machine element. This is coupled to the actuator for this purpose. If a linear movement of the component is also to be detected, then not only a sliding potentiometer is required, but also a complex coupling mechanism that only transmits the rotary movement to the rotary potentiometer and the linear movement to the sliding potentiometer.

DE-AS 23 17 144 describes a device for adjusting several resistors using an adjustment lever pivoted by a ball. This allows displacements of the adjustment lever in the xy direction to be recorded, but not rotations around its long axis. A similar device is described in DE-OS 21 62 853.

Contactless arrangements, for example electrodynamic systems such as differential transformers, inductive or capacitive devices or pneumatic dynamic pressure arrangements, are known for detecting rotary and sliding movements. However, the circuitry effort involved in such arrangements is high. In addition, the achievable signal voltages or signal currents are very small in relation to the supply voltage or supply current. This makes such arrangements sensitive to interference.

The object of the invention is to develop a rotary potentiometer of the type mentioned at the beginning in such a way that the actuator can also carry out and detect linear movements.

According to the invention, the above object is achieved in a rotary potentiometer of the type mentioned at the outset in that the actuator is displaceable by a stroke axially to the cylinder axis relative to the resistance track, that the axial width of the resistance track corresponds to the stroke of the actuator, that at least one further pair of electrodes is provided on the two edges of the resistance track running in the circumferential direction of the cylinder, and that the two pairs of electrodes are alternately supplied with voltage.

The actuator can thus detect or extend movements with rotary and linear movement components. The slider takes up a corresponding position on the resistance track. By alternately switching the pair of electrodes on the edges parallel to the cylinder axis and the pair of electrodes on the edges running in the circumferential direction, the resistance corresponding to the rotary movement and the linear movement becomes effective in time with the voltage change.

The structure is compact because the number of moving components is low.

A further advantage is that the voltage sensed at the resistance track S is essentially equal to the maximum value of the

applied supply voltage and the intermediate values represent a corresponding part of the supply voltage. In comparison to contactless devices, high voltages can therefore be achieved, so that the arrangement is comparatively insensitive to interference.

In a preferred embodiment of the invention, the resistance is homogeneous over the entire resistance path. The tapped voltage is therefore directly proportional to the respective displacement setting and the respective rotational position.

In one embodiment of the invention, the resistance track is provided on the inner circumference of a housing part and the actuator is mounted in its center. This means that a large area of the potentiometer is available for the resistance track. However, it is also possible to

To provide a standing track on an inner cylindrical part and as

It is not necessary for the actuator to be moved by the component whose movement is to be detected. The component can just as easily move the resistance path relative to the actuator.

«I Mil · · ·«

• * * ~ t t I 141«

&bull;··<·*&diams;&Pgr;*»# I · Ii ft·

I I

I I I

In order to avoid linearity distortions over the entire rotation or stroke range, several pairs of electrodes are arranged at each edge of the resistance track, whereby the electrodes are short compared to the length of the edges. The electrodes are decoupled by means of diodes. Such an arrangement of electrode pairs is described in DE-OS 32 43.

The production of a suitable resistance track in reverse laminated chulk is described in DE-OS 33 22 382.

The rotary potentiometer described can be used, for example, in actuating devices that perform rotary and sliding movements and for which position feedback is desired. Such actuating devices are, for example, control handles, valve actuating devices, locking systems or control units for manual transmissions.

Further advantageous embodiments of the invention will become apparent from the following description.
20

Tn of the drawing show:

Figure 1 shows a longitudinal section of a potentiometer, Figure 2 shows a section along the line TT-TT according to Figure 1,

Figure 3 shows schematically a resistance track in an unwound position,

&psgr;&PSgr; VV VV ■* PVVV

} &iacgr; ¹ !',. ¹ V .'

Figure 4 a carrier with resistance track and tapping field

in a settled situation
and

Figure 5 shows a circuit diagram.
5

' A cylindrical, tubular housing part (1) is closed with two covers (2, 3). Bearings (4, 5) for a shaft (6) are arranged on the covers (2, 3). The shaft (6) extends concentrically [.

to the cylinder axis (7) of the housing part (1). |

A carrier film (8) is arranged on the inside of the housing part (1), which

a resistance track (9) and a tapping field (10). The resistance [

ϳ f

track (9) extends over an angle of less than 180 . It has a width (B). The tapping field (10) is located on the inner circumference of the housing part (1) opposite the resistance track (9) and has the same surface area as this.

An actuator (11) is held on the shaft (6) and carries a wiper (12). A wiper tongue (13) of the wiper (12) rests on the resistance track (9). A wiper tongue (14) of the wiper (12) rests on the tapping field (10). The shaft (8) and the wiper (12) are not only rotatable about the cylinder axis (7). They are also axially displaceable by a stroke (H). The stroke (H) is essentially equal to the width (B) of the resistance track (9).

·· ·· II III

In the embodiment shown in Figure 3, an electrode (17, 18) is arranged on each of the edges (15, 16) parallel to the cylinder axis (7). The electrodes (17, 18) form an electrode pair. They extend essentially continuously over the relevant edge (15 or 16). 5

Electrodes (21, 22) are provided on the two edges (19, 20) of the resistance track (9) running in the circumferential direction of the cylindrical housing (1), forming a further pair of electrodes. The electrodes (21, 22) are point-shaped compared to the length of the edges (19, 20).

The electrode pairs (16, 17; 21, 22) are alternately connected to a DC voltage source (24) via a switch (23) (see Figure 5), which supplies a supply voltage. In the arrangement according to Figure 3, sufficient linearity of the resistance curve is guaranteed in the direction of the rotary movement (D). In the direction of the stroke (H), however, the resistance curve depends on the respective rotary position. One way of reporting this is shown in the resistance track (9) according to Figure 4.

The resistance track (9) according to Figure 3 is rectangular. Its longer extension is intended for the rotary movement (D). However, it would also be possible to assign the longer extension to the stroke (H).

In the embodiment according to Figure 4, the resistance track (9) is square. A plurality of electrodes (17, 18, 21, 22) are provided on each of the edges (15, 16, 19, 20). The electrodes are short in comparison to the length of the edges (15, 16). The contact surface with which the

The wiper end (13) rests on the resistance track (9) and is small compared to the distance between the electrodes. The electrodes are the same distance from each other.

The electrodes (17) are connected to a conductor track (26) of the carrier foil (8) via diodes (25). The electrodes (21) are connected to the conductor track (26) via diodes (27). The electrodes (22) are connected to another conductor track (29) via diodes (28). The electrodes (18) are connected to the conductor track (29) via diodes (30). The diode (27) and the diodes (28) on the one hand and the diodes (30) and the diodes (25) on the other hand are polarized in the same direction, but in such a way that the diodes (25) are polarized in opposite directions with respect to the neighboring diodes (27) of the same conductor track (26).

A resistor (Rl) is arranged between the conductor track (26) and its connection point (31) and a resistor (R2) is arranged between the conductor track (29) and its connection point (32). The resistors (Rl, R2) compensate for the temperature response of the diodes.

The square shape of the resistance track (9) has the advantage that the same diodes can be used on all electrodes and the same resistors (Rl, R2) on both conductor tracks, whereby the same voltage ratios result during the rotary movement and during the lifting movement.

Another advantage of the arrangement according to Figure 4 is that, in addition to the two connection points (31, 32), only one further connection point (33) needs to be provided for the tapping field (10).

. loo

&bull; · · t · Il Il t · * *

&bull;&bull;&bull;&bull;&bull;II·«·*·# ·· *· &diams; · III! ·* * · 4 t

.",i &iacgr;&ogr; -.

In Figure 5, RH is the resistance of the resistance track (9) acting in the stroke direction. RD is the resistance of the resistance track (9) acting in the rotation direction. An evaluation circuit (34) is connected to the connection point (33) which, in accordance with the cycle of the switching device (23), alternately detects the voltage tapped at the resistor (RH) and the resistor (RD), which corresponds to the displacement position of the slider (12) in the stroke direction or the rotation of the slider (12) in the rotation direction.

The functionality of the described rotary slide potentiometer is essentially as follows:

If the shaft (6) is coupled to a component that rotates around an axis on the one hand and moves in the axial direction on the other, then the slider (12) performs a corresponding movement on the resistance track (9). The evaluation circuit (34) records voltages corresponding to the respective rotational position and the respective displacement position. In order to enable an exact evaluation, the cycle with which the changeover switch (23) alternately applies the supply voltage to the electrode pairs (17, 18 or 21, 22) is faster than the speed of the movement.

In other embodiments it is also possible to use the resistance*

&ogr;
track (9) to extend practically over 360. The tapping field (10) can then be arranged in the axial direction of the housing part (1) next to the resistance track (9). However, instead of the tapping field (10), it is also possible to tap the voltage detected by the wiper (12), e.g. by means of another wiper on the actuator (11) or the shaft (6) or to guide it to the housing (1) by means of a spiral spring.

- 11 -

&bull; · · « I I I I 1 I I . S

ft,, <&igr;&igr;«·

To compensate for the temperature-dependent diode voltage, the known temperature coefficient of the diode voltage can also be compensated in the evaluation circuit (34) using the temperature-dependent resistors. Temperature compensation can also be achieved by switching the voltage drop across the diodes to the evaluation circuit (34) via an additional measuring line.

In the case of rectangular, non-square, homogeneous resistance paths (9), the voltage drop across the resistors (Rl, R2) used for compensation is different, so that they only insufficiently compensate for the temperature-dependent diode forward voltage. To compensate for this, either the two resistors (Rl, R2) can have correspondingly different values or the current flowing through them can be selected differently by applying a different supply voltage.

- 12 -

11 ·* ·

Reference number list 02/86 GM

1 Housing part 26 Conductor track 2 Lid 27 Diodes 3 Lid 28 Diodes 4 Storage location 29 Conductor track 5 Storage location 30 Diodes 6 Wave 31 Junction 7
r MmJ II IfUVf «Vll^e 32 Anerhiiiflctpiip 8th Carrier film 33 Junction 9 Resistance track 34 Evaluation circuit 10 Tapping field 11 Actuator RD Resistance in direction of rotation 12 grinder RH Resistance in stroke direction 13 Schi elferzunge Rl Resistance 14 Schi elferzunge R2 Resistance 15 Edge parallel to 7 D rotational movement 16 Edge parallel to 7 H Hub 17 electrode B Width of the resistance base 18 electrode 19 Edge 1n circumferential direction 20 Edge 1n circumferential direction 21 electrode 22 electrode 23 Switch 24 DC voltage source 25 Diodes

7.13. -

Claims (1)

&bull; A · · t &Lgr; 3*11 ·· · ·■ Al �Iα J * P r e h Electro-precision mechanical works Jakob Proh, Nachf. GmbH S Co. Schweinfurter Strasse 5 Bad Neustadt/Saale, 02.03.88 02/88 GM claims Rotary potentiometer 1. Rotary potentiometer with a cylindrical or partially cylindrical resistance track, on the two edges of which parallel to the cylinder axis at least one pair of electrodes is arranged, via which the resistance track is subjected to voltage and with a wiper lying on the resistance track, which is held on an actuator rotatable about the cylinder axis,
characterized, that the actuator (11) is displaceable by a stroke (H) axially to the cylinder axis (7) relative to the resistance track (9), that the axial width (B) of the resistance track (9) corresponds to the stroke (H) of the actuator (U), that at least one further pair of electrodes (21; 22) is provided on the two edges (19, 20) of the resistance track (9) running in the circumferential direction of the cylinder and that the two pairs of electrodes (17, 18; 21, 22) are alternately supplied with voltage. 2. Rotary potentiometer according to claim 1,
characterized, that the resistance path (9) is homogeneous. 3i Rotary potentiometer according to claim 1 or 2, characterized in that that the resistance track (9) is mounted on the inner circumference of a housing part (1) and the actuator (il) is mounted in its center. 4. Rotary potentiometer according to one of the preceding claims, characterized, &ogr; that the resistance track (9) extends over less than 180 and the wiper (12) is assigned a tapping field (10) which has the same area as the resistance track (9) and is arranged diametrically to the resistance track (9). 5. Rotary potentiometer according to one of the preceding claims, characterized in that several pairs of electrodes (17, 18; 21, 22) are arranged on the edges (15, 16, 19, 20) of the resistance track (9), the electrodes being short in comparison to the length of the edges (15, 16, 19, 20), and that the electrodes (17, 18, 21, 22) are decoupled by means of diodes (25, 27, 28, 30). 6. Rotary potentiometer according to claim 5, characterized in that resistors (R1, R2) with a positive temperature coefficient are provided to compensate for the temperature-dependent forward voltage of the diodes (25, 27, 28, 30). 7. Rotary potentiometer according to claim 5 or 6, characterized in that the contact surface with which the wiper (12) rests on the wiper track (9) is smaller than the distance between adjacent electrodes (17, 18, 21, 22). 8. Rotary potentiometer according to one of the preceding claims, characterized in that the resistance band (9) is square in its development